482 



MEMOIR OF DANIEL TREADWELL 



An Elevation in Section of the Device for Fieing Cannon, 



a A represents a portion of the breech of a gun. b is a steel plug screwed into 

 the gun, through which the vent a is bored, and extending into the calibre. The upper 

 or outer part of the vent is enlarged to form a recess or chamber, b, into which the 

 priming cap is placed, c is a strong lever called a " sett stock," which is jointed at 

 one end to the stud D, screwed into the gun, which permits the other end to be turned 

 back from the vent out of the way ; in the end over the vent is a steel set or punch, c, 

 the lower end of which fits close in the socket b ; the other end passes up through the 



stock, and has upon it a screwed 



The sett is made with a shoulder 



bears against the under side of the sett stock, and fits it loosely. This sett serves th 



purpose of a vent stopper and 



S 



the primer 



This end of 



the sett stock is held down by the button e, which is a disk of steel having a segment 

 cut off from one side, and rotating upon the steel bolt f by means of a handle (not 

 shown in the figure) screwed into it. The button rests upon a lock-piece, g, secured to 

 the gun. The underside of g is made for a part of its circumference in the form of a 

 helical wedge, or inclined like a portion of a square screw thread. When the button 

 is turned by the handle, the inclined surface g passes over the lip h, which is also bev- 

 elled to correspond to it, and forces the sett e down upon the cap J, and holds it firmly 

 against the force of the discharge. I is a hammer moved by a lanyard, as is common. 



the primer, also shown separately. It is made of two disks of copper 



th 



pper 



made thin, and has its edge turned down outside of the lower one, Jc, fitti 



closely to it. B 



these disks the fulminate, m, is placed. In the centre of 



disk h is a small hole, into which the quill 



paper 



/ 



placed fur hold 



o 



the 





